Tonight, Mitt Romney formally accepts the Republican Party's nomination to be president of the United States. The path to a presidential nomination is never smooth. But by Republican Party standards, this year's primary campaign was pretty choppy. NPR's Ari Shapiro has this look back.

ARI SHAPIRO, BYLINE: Mitt Romney launched this campaign on June 2nd, 2011, at a farm in New Hampshire.

MITT ROMNEY: And in the campaign to come, the American ideals of economic freedom and opportunity need a clear and unapologetic defense. And I intend to make it because I have lived it.

SHAPIRO: He was the favorite to win the nomination, even at that point; the establishment candidate. At Harvard's Institute of Politics, Trey Grayson moderated a panel on the race.

TREY GRAYSON: And at the end, I asked a bunch of national journalists, who's going to be the Republican nominee? And they all - went through and said, Mitt Romney.

SHAPIRO: After losing in 2008, Romney was next in line for 2012. That kind of order is the way it's always been, in the Republican Party. But this time, things looked different. Joe Alleck(ph) came from New Jersey to a rally on the National Mall in Washington, just before the 2010 midterm elections.

JOE ALLECK: Said we're not going to buy the lies anymore. Every politician wants us to buy into them so that they stay in power. That's going to stop.

SHAPIRO: That boisterous energy powered Republicans to take over the House, on an insurgent Tea Party wave. President Obama was no longer the untouchable superstar.

PRESIDENT BARACK OBAMA: I'm not recommending for every future president, that they take a shellacking like they did - like I did last night.

SHAPIRO: The credit for that shellacking went to activists who had no loyalty to Republican Party leaders. When candidates started lining up for the 2012 presidential race, voters were not looking for a primary coronation - especially when the heir to the throne was Mitt Romney, a New England blue-stater. Ben Smith is a retiree from Mount Pleasant, South Carolina.

BEN SMITH: I think he's a liberal in GOP clothing. He'd have to be, to survive in Massachusetts.

SHAPIRO: The first big test came just over a year ago in Ames, Iowa. Mitt Romney hardly competed, in the straw poll. The winner was the leader of the Tea Party caucus in the House of Representatives.

SHAPIRO: It was not on to all 50 states, for Bachmann. She was the first in a string of "Angry Birds" candidates. One by one, they soared to the top of the polls - then crashed down to Earth. The day Bachmann won the Ames straw poll, another man entered the race on a rocket trajectory. And within months, Rick Perry tripped over his tongue at a debate, and his candidacy fizzled.

GOV. RICK PERRY: The third agency of government - I would do away with the Education, the...

REP. RON PAUL: Commerce.

PERRY: Commerce and - let's see. I can't; the third one, I can't. Sorry. Oops.

SHAPIRO: Up from the ashes rose another anti-establishment candidate with Tea Party credentials, and a catchy tax plan.

HERMAN CAIN: The 999 plan that I have proposed is simple, transparent, efficient, fair and neutral.

SHAPIRO: A sex scandal forced Herman Cain out of the race before a single vote was cast. From his perch at Harvard, Republican Trey Grayson marveled at the parade.

GRAYSON: They kept coming. It was like - you know, it was like a zombie movie. You know, you think you got him, and then the next one comes at you, and the next one comes at you. It's like, come on, the zombie's dead now - no, it's not.

SHAPIRO: All the while, Romney chugged along. No wild, up-and-down swings for him; just a steady strategy that he described this way, on the day of the Michigan primary.

ROMNEY: You know, I'm not willing to light my hair on fire, to try and get support. I am who I am.

SHAPIRO: Month after month, his stump speeches hit the same key point.

ROMNEY: As president, I will get our economy back on track, and get our citizens back to work.

SHAPIRO: Alice Stewart was a spokesman for Michele Bachmann and later, Rick Santorum. Now, she does surrogate work for the Romney campaign.

ALICE STEWART: No matter what was going on, no matter what the news of the day was, he was laser-focused on discussing the economy, and his plan to create jobs and turn this economy around. And that being the issue number one in this campaign, that's been the key to his success.

SHAPIRO: There was also another key to his success, one that Romney inadvertently demonstrated at a Mississippi campaign stop.

ROMNEY: Oh, look at that. Look at that little guy. There - got him. It wasn't really a cockroach, I promise.

SHAPIRO: When a rival crossed Romney's path, the campaign would set out to squish him like a bug. That's one of advantage to being the establishment candidate - Romney had millions of dollars to spend, drowning his opponents in attack ads.

(SOUNDBITE OF POLITICAL AD)

UNIDENTIFIED ANNOUNCER: Newt has a ton of baggage. Santorum voted to raise the debt limit five times. Rick Perry not only supports amnesty but gave illegals in-state tuition. Gingrich was fined $300,000 by a Republican Congress, for ethics violations.

SHAPIRO: The money mattered, but Rick Santorum and Newt Gingrich had their own wealthy underwriters. And they were both persistent. Santorum won Iowa by just a few votes. Gingrich carried South Carolina in a landslide. So by the time the primary race came to Florida, in late January, Romney's inevitability seemed a bit less inevitable. Out of the first three states, he had only won New Hampshire. Along with the attack ads, a fiery debate performance in Florida helped put Romney's campaign back on track.

ROMNEY: And Mr. Speaker, I know that sounds like an enormous revelation. But have you checked your own investments? You also have investments from mutual funds that also invest in Fannie Mae and Freddie Mac.

NEWT GINGRICH: Right.

(CHEERS

SHAPIRO: Sometimes, Romney's worst enemies seemed not to be the other candidates. It was his own tendency to say the wrong thing. By now, the lines have become notorious - even though some were distorted, and taken out of context.

(SOUNDBITE OF VARIOUS BROADCASTS)

UNIDENTIFIED PROTESTER: Corporations.

ROMNEY: Corporations are people, my friend...

...I like being able to fire people that provide services to me...

...I'm not concerned about the very poor. We have a safety net there. If it needs repair, I'll fix it...

...Ann drives a couple of Cadillacs, actually. And...

SHAPIRO: Romney overcame his adversaries, external and internal. And just before the Pennsylvania primary in April, his last rival - Rick Santorum - finally dropped out. Romney declared victory back in New Hampshire, the state where he first launched this race.

ROMNEY: To all of the thousands of good and decent Americans I've met, who want nothing more than a better chance, a fighting chance; to all of you, I have a simple message. Hold on a little longer; a better America begins tonight.

(CHEERS)

SHAPIRO: But parts of the Republican base still weren't swooning. In April, Romney attended a Tea Party rally in Philadelphia, where voter Bill Miller tried to overcome his skepticism.

BILL MILLER: At this point, the only thing he can possibly do is - who he picks for VP; who's going to be his people that he's going to work with, going forward.

SHAPIRO: Romney got the memo.

(SOUNDBITE OF TWISTED SISTER SONG, "WE'RE NOT GONNA TAKE IT")

PAUL RYAN: Hey, hey, hey. Hey. How about it, huh? Man!

SHAPIRO: His running mate, Paul Ryan, is a Tea Party favorite who brings youth, energy, and a we're-not-going-to-take-it sense of excitement to the presidential ticket. And now, Romney has gone from presumptive nominee to official nominee. The Republican establishment, and the Tea Party zeal, are both behind his ticket. All that's left to win, is the undecided voters - and the presidential election itself.